/*-------------------------------------------------------------------------
 *
 * parse_param.c
 *      handle parameters in parser
 *
 * This code covers two cases that are used within the core backend:
 *        * a fixed list of parameters with known types
 *        * an expandable list of parameters whose types can optionally
 *          be determined from context
 * In both cases, only explicit $n references (ParamRef nodes) are supported.
 *
 * Note that other approaches to parameters are possible using the parser
 * hooks defined in ParseState.
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      src/backend/parser/parse_param.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <limits.h>

#include "catalog/pg_type.h"
#include "nodes/nodeFuncs.h"
#include "parser/parse_param.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"


typedef struct FixedParamState
{
    Oid           *paramTypes;        /* array of parameter type OIDs */
    int            numParams;        /* number of array entries */
} FixedParamState;

/*
 * In the varparams case, the caller-supplied OID array (if any) can be
 * re-palloc'd larger at need.  A zero array entry means that parameter number
 * hasn't been seen, while UNKNOWNOID means the parameter has been used but
 * its type is not yet known.
 */
typedef struct VarParamState
{
    Oid          **paramTypes;        /* array of parameter type OIDs */
    int           *numParams;        /* number of array entries */
} VarParamState;

static Node *fixed_paramref_hook(ParseState *pstate, ParamRef *pref);
static Node *variable_paramref_hook(ParseState *pstate, ParamRef *pref);
static Node *variable_coerce_param_hook(ParseState *pstate, Param *param,
                           Oid targetTypeId, int32 targetTypeMod,
                           int location);
static bool check_parameter_resolution_walker(Node *node, ParseState *pstate);
static bool query_contains_extern_params_walker(Node *node, void *context);


/*
 * Set up to process a query containing references to fixed parameters.
 */
void
parse_fixed_parameters(ParseState *pstate,
                       Oid *paramTypes, int numParams)
{
    FixedParamState *parstate = palloc(sizeof(FixedParamState));

    parstate->paramTypes = paramTypes;
    parstate->numParams = numParams;
    pstate->p_ref_hook_state = (void *) parstate;
    pstate->p_paramref_hook = fixed_paramref_hook;
    /* no need to use p_coerce_param_hook */
}

/*
 * Set up to process a query containing references to variable parameters.
 */
void
parse_variable_parameters(ParseState *pstate,
                          Oid **paramTypes, int *numParams)
{
    VarParamState *parstate = palloc(sizeof(VarParamState));

    parstate->paramTypes = paramTypes;
    parstate->numParams = numParams;
    pstate->p_ref_hook_state = (void *) parstate;
    pstate->p_paramref_hook = variable_paramref_hook;
    pstate->p_coerce_param_hook = variable_coerce_param_hook;
}

/*
 * Transform a ParamRef using fixed parameter types.
 */
static Node *
fixed_paramref_hook(ParseState *pstate, ParamRef *pref)
{
    FixedParamState *parstate = (FixedParamState *) pstate->p_ref_hook_state;
    int            paramno = pref->number;
    Param       *param;

    /* Check parameter number is valid */
    if (paramno <= 0 || paramno > parstate->numParams ||
        !OidIsValid(parstate->paramTypes[paramno - 1]))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_PARAMETER),
                 errmsg("there is no parameter $%d", paramno),
                 parser_errposition(pstate, pref->location)));

    param = makeNode(Param);
    param->paramkind = PARAM_EXTERN;
    param->paramid = paramno;
    param->paramtype = parstate->paramTypes[paramno - 1];
    param->paramtypmod = -1;
    param->paramcollid = get_typcollation(param->paramtype);
    param->location = pref->location;

    return (Node *) param;
}

/*
 * Transform a ParamRef using variable parameter types.
 *
 * The only difference here is we must enlarge the parameter type array
 * as needed.
 */
static Node *
variable_paramref_hook(ParseState *pstate, ParamRef *pref)
{
    VarParamState *parstate = (VarParamState *) pstate->p_ref_hook_state;
    int            paramno = pref->number;
    Oid           *pptype;
    Param       *param;

    /* Check parameter number is in range */
    if (paramno <= 0 || paramno > INT_MAX / sizeof(Oid))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_PARAMETER),
                 errmsg("there is no parameter $%d", paramno),
                 parser_errposition(pstate, pref->location)));
    if (paramno > *parstate->numParams)
    {
        /* Need to enlarge param array */
        if (*parstate->paramTypes)
            *parstate->paramTypes = (Oid *) repalloc(*parstate->paramTypes,
                                                     paramno * sizeof(Oid));
        else
            *parstate->paramTypes = (Oid *) palloc(paramno * sizeof(Oid));
        /* Zero out the previously-unreferenced slots */
        MemSet(*parstate->paramTypes + *parstate->numParams,
               0,
               (paramno - *parstate->numParams) * sizeof(Oid));
        *parstate->numParams = paramno;
    }

    /* Locate param's slot in array */
    pptype = &(*parstate->paramTypes)[paramno - 1];

    /* If not seen before, initialize to UNKNOWN type */
    if (*pptype == InvalidOid)
        *pptype = UNKNOWNOID;

    param = makeNode(Param);
    param->paramkind = PARAM_EXTERN;
    param->paramid = paramno;
    param->paramtype = *pptype;
    param->paramtypmod = -1;
    param->paramcollid = get_typcollation(param->paramtype);
    param->location = pref->location;

    return (Node *) param;
}

/*
 * Coerce a Param to a query-requested datatype, in the varparams case.
 */
static Node *
variable_coerce_param_hook(ParseState *pstate, Param *param,
                           Oid targetTypeId, int32 targetTypeMod,
                           int location)
{// #lizard forgives
    if (param->paramkind == PARAM_EXTERN && param->paramtype == UNKNOWNOID)
    {
        /*
         * Input is a Param of previously undetermined type, and we want to
         * update our knowledge of the Param's type.
         */
        VarParamState *parstate = (VarParamState *) pstate->p_ref_hook_state;
        Oid           *paramTypes = *parstate->paramTypes;
        int            paramno = param->paramid;

        if (paramno <= 0 ||        /* shouldn't happen, but... */
            paramno > *parstate->numParams)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_PARAMETER),
                     errmsg("there is no parameter $%d", paramno),
                     parser_errposition(pstate, param->location)));

        if (paramTypes[paramno - 1] == UNKNOWNOID)
        {
            /* We've successfully resolved the type */
            paramTypes[paramno - 1] = targetTypeId;
        }
        else if (paramTypes[paramno - 1] == targetTypeId)
        {
            /* We previously resolved the type, and it matches */
        }
        else
        {
            /* Oops */
            ereport(ERROR,
                    (errcode(ERRCODE_AMBIGUOUS_PARAMETER),
                     errmsg("inconsistent types deduced for parameter $%d",
                            paramno),
                     errdetail("%s versus %s",
                               format_type_be(paramTypes[paramno - 1]),
                               format_type_be(targetTypeId)),
                     parser_errposition(pstate, param->location)));
        }

        param->paramtype = targetTypeId;

        /*
         * Note: it is tempting here to set the Param's paramtypmod to
         * targetTypeMod, but that is probably unwise because we have no
         * infrastructure that enforces that the value delivered for a Param
         * will match any particular typmod.  Leaving it -1 ensures that a
         * run-time length check/coercion will occur if needed.
         */
        param->paramtypmod = -1;

        /*
         * This module always sets a Param's collation to be the default for
         * its datatype.  If that's not what you want, you should be using the
         * more general parser substitution hooks.
         */
        param->paramcollid = get_typcollation(param->paramtype);

        /* Use the leftmost of the param's and coercion's locations */
        if (location >= 0 &&
            (param->location < 0 || location < param->location))
            param->location = location;

        return (Node *) param;
    }

    /* Else signal to proceed with normal coercion */
    return NULL;
}

/*
 * Check for consistent assignment of variable parameters after completion
 * of parsing with parse_variable_parameters.
 *
 * Note: this code intentionally does not check that all parameter positions
 * were used, nor that all got non-UNKNOWN types assigned.  Caller of parser
 * should enforce that if it's important.
 */
void
check_variable_parameters(ParseState *pstate, Query *query)
{
    VarParamState *parstate = (VarParamState *) pstate->p_ref_hook_state;

    /* If numParams is zero then no Params were generated, so no work */
    if (*parstate->numParams > 0)
        (void) query_tree_walker(query,
                                 check_parameter_resolution_walker,
                                 (void *) pstate, 0);
}

/*
 * Traverse a fully-analyzed tree to verify that parameter symbols
 * match their types.  We need this because some Params might still
 * be UNKNOWN, if there wasn't anything to force their coercion,
 * and yet other instances seen later might have gotten coerced.
 */
static bool
check_parameter_resolution_walker(Node *node, ParseState *pstate)
{// #lizard forgives
    if (node == NULL)
        return false;
    if (IsA(node, Param))
    {
        Param       *param = (Param *) node;

        if (param->paramkind == PARAM_EXTERN)
        {
            VarParamState *parstate = (VarParamState *) pstate->p_ref_hook_state;
            int            paramno = param->paramid;

            if (paramno <= 0 || /* shouldn't happen, but... */
                paramno > *parstate->numParams)
                ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_PARAMETER),
                         errmsg("there is no parameter $%d", paramno),
                         parser_errposition(pstate, param->location)));

            if (param->paramtype != (*parstate->paramTypes)[paramno - 1])
                ereport(ERROR,
                        (errcode(ERRCODE_AMBIGUOUS_PARAMETER),
                         errmsg("could not determine data type of parameter $%d",
                                paramno),
                         parser_errposition(pstate, param->location)));
        }
        return false;
    }
    if (IsA(node, Query))
    {
        /* Recurse into RTE subquery or not-yet-planned sublink subquery */
        return query_tree_walker((Query *) node,
                                 check_parameter_resolution_walker,
                                 (void *) pstate, 0);
    }
    return expression_tree_walker(node, check_parameter_resolution_walker,
                                  (void *) pstate);
}

/*
 * Check to see if a fully-parsed query tree contains any PARAM_EXTERN Params.
 */
bool
query_contains_extern_params(Query *query)
{
    return query_tree_walker(query,
                             query_contains_extern_params_walker,
                             NULL, 0);
}

static bool
query_contains_extern_params_walker(Node *node, void *context)
{
    if (node == NULL)
        return false;
    if (IsA(node, Param))
    {
        Param       *param = (Param *) node;

        if (param->paramkind == PARAM_EXTERN)
            return true;
        return false;
    }
    if (IsA(node, Query))
    {
        /* Recurse into RTE subquery or not-yet-planned sublink subquery */
        return query_tree_walker((Query *) node,
                                 query_contains_extern_params_walker,
                                 context, 0);
    }
    return expression_tree_walker(node, query_contains_extern_params_walker,
                                  context);
}
